1. Field of the Invention
The present invention relates to a sample chamber which is maintained in high vacuum around a sample through evacuation therefrom and a circuit pattern forming apparatus using the same.
2. Conventional Art
In an apparatus which forms or inspects circuit patterns such as for a semiconductor device and a magnetic head and circuit patterns such as masks and reticles for forming circuit patterns for a semiconductor device, these circuit patterns are formed and inspected through irradiation of charged particles onto samples. In such instance, it is unavoidable that the charged particles, in particular electron beams have to be used in vacuum. For this reason, the circuit pattern formation and inspection is performed while placing samples in a gas evacuated vacuum chamber.
Hereinbelow, an electron beam pattern drawing apparatus which draws a circuit pattern on a sample by making use of electron beams will be explained taking up as an example.
An electron beam pattern drawing apparatus is one in which through generation of electron beams under a super high vacuum environment and scanning therewith LSI patterns are formed on a semiconductor substrate or a glass substrate called as a mask which is used for an exposure apparatus such as a stepper.
FIG. 12 shows a structure of a conventional electron beam pattern drawing apparatus. As shown in FIG. 12, electron beams 3 emitted from an electron gun 2 in a column 1 are shaped into a rectangular shape by a diaphragm 4 and a shaping deflector 5, and are image-formed on a desired position of a sample 8 by an electron lens 6 and a deflector 7. The sample 8 is fixed on an XY stage 9 through a sample holder or directly.
The position of the sample 8 on the XY stage 9 is managed by measuring the distance between a bar mirror 13 and a laser interference meter 12, and through feed forwarding the obtained information to the deflector 7 a highly accurate circuit pattern can be formed. Inside of a sample chamber 10 is kept in a high vacuum environment by a sample chamber use vacuum pump 17 to thereby prevent energy loss of the electron beams.
Now, a transportation route of the sample 8 will be explained.
The sample 8 is transported by a transportation device 16 in a load chamber 14 located adjacent to the sample chamber 10 from external in atmospheric circumstance into the load chamber 14, which is preliminarily gas-evacuated from atmospheric state into vacuum state a load chamber use vacuum pump 18. When the vacuum in the load chamber 14 reaches at the same level as that in sample chamber 10, a valve 15 is opened and the sample 8 is transported onto the XY stage 9. After completing pattern drawing, a reverse route is traced, in that inside of the load chamber 14 is returned from vacuum into atmospheric circumstance and thereafter, the sample 8 is transported into outside. With the above series of operations, the transportation of the sample can be carried out while keeping the sample chamber 10 in vacuum state, thereby, an improvement of throughput is achieved.
During drawing of a circuit pattern by an electron beam pattern drawing apparatus, it is necessary to keep the electron beam passage in high vacuum so as to prevent energy loss of the electron beams as has been referred to above, however, there were the following problems in conventional apparatuses.
(1) It was required to evacuate the entire sample chamber in high vacuum, therefore, a vacuum pump of high performance as well as large capacity was indispensable.
(2) Once the inside of the sample chamber was placed in atmospheric circumstance due to such as maintenance and failure thereof, it took a few hours to restore the circumstance into high vacuum which reduced available time of the apparatus.
(3) In order to keep the inside of the sample chamber in high vacuum, parts used inside the sample chamber were restricted to inactive materials and, in particular, many kinds of resins and lubricants could not be used.
(4) Mechanism which use gas such as air could not be mounted in the sample chamber.
In order to overcome the above problems, until now apparatuses which keep around the passage of the electron beams and a part of the stage in vacuum state are, for example, disclosed in JP-A-1-128525 (1989), JP-A-8-17709 (1996) and JP-B-3-23631 (1991). These apparatuses are provided with a flange 60 which includes a function of vacuum evacuation at the bottom face of the column 1 as shown in FIG. 13 and perform differential evacuation while managing the gap between the sample 8 and the flange 60.
In the flange 60 apertures 60A for vacuum evacuation are formed which permits differential evacuation with the circumference of the stage 9.
However, in the apparatuses as disclosed such as in JP-A-1-128525 (1989), JP-A-8-17709 (1996) and JP-B-3-23631 (1991), although it is possible to keep the electron beam passage in vacuum upto the sample 8 regardless to the atmosphere of the stage 9, a pressure difference due to a local differential evacuation is caused on the sample 8. Accordingly, at a top table 21 the region of the pressure difference varies in accordance with the displacement of the sample 8 which possibly causes attitude change of the top table 21 and deformation thereof.
Further, when performing pattern drawing (exposure, inspection) over the entire surface of a sample, because of the existence of a gap between edges of the sample 8 and a sample holding mechanism or the top table 21, amount of gas which flows in through the gap increases which makes difficult to obtain a stable vacuum. Namely, in order to keep a stable differential evacuation condition it is necessary to prevent the apertures 60A from protruding beyond the outer circumference of the sample 8 as shown in FIG. 13. As a result, in a range of distance R from outer circumference of the sample 8 toward the center thereof a pattern drawing can not be performed, thereby, a possible pattern drawing range around the outer circumference of the sample is wasted and a yielding of the sample 8 with regard to pattern drawing range is reduced.
An object of the present invention is to provide an evacuation use sample chamber which performs a stable evacuation and keeps around a sample at a predetermined high vacuum and a circuit pattern forming apparatus which permits a highly accurate pattern drawing over the entire region of the sample.
In order to achieve the above object, an evacuation use sample chamber according to the present invention is characterized, in that the evacuation use sample chamber is constituted by a table which is provided with a recessed portion disposed in a sample chamber main body and for mounting a sample and a groove portion surrounding the recessed portion; a stage which holds the table and is displaceable in front and back, right and left and up and down directions together with the table; a sample chamber cover which covers above the sample chamber main body including the table; and an evacuation use pipe which communicates with the groove portion and evacuates gas between the bottom face of the sample chamber cover and the top face of the table including the sample.
More specifically, the present invention provides the following sample chamber and device.
The present invention provides an evacuation use sample chamber which is characterized by comprising, a sample chamber main body; a table which is provided with a recessed portion disposed in the sample chamber main body and for mounting a sample and a groove portion surrounding the recessed portion; a stage which holds the table and is displaceable in front and back, right and left and up and down directions together with the table; a sample chamber cover which covers above the sample chamber main body including the table; and an evacuation use pipe which communicates with the groove portion and evacuates gas between the bottom face of the sample chamber cover and the top face of the table including the sample.
Preferably, the evacuation use sample chamber comprises a pressure gauge which permits measurement of pressure in a region surrounded by the sample chamber cover, the table and a passage of charged particle beams to be irradiated onto the sample.
Preferably, the sample chamber cover is provided with an open and close cover which opens and closes the passage of the charged particle beams to be irradiated onto the sample.
Preferably, the evacuation use sample chamber is provided with a means which evacuates a region surrounded by the sample chamber cover, the table, the passage of the charged particle beams and the open and close cover, measures pressure therein with the pressure gauge and operates the open and close cover after the measured pressure reaches at a same level as in a passage other than the region of the charged particle beams.
Preferably, the sample table includes a sample up and down moving mechanism which is used when transporting the sample.
Preferably, the height of the upper face at the outer circumferential side from the groove portion of the table is selected higher than the upper face at the inner circumferential side from the groove portion.
With the above structure, differential evacuation between the bottom face of the sample chamber cover and the top face of the table can be performed, thereby, the atmosphere around the sample can be kept in high vacuum. Further, since the inside of the groove which can always be evacuated is in vacuum condition, a pressure difference acting on the sample and the table is kept constant regardless to the movement of the sample. Thereby, the attitude accuracy of the table and the deformation state thereof are kept constant during pattern drawing. In the present specification xe2x80x9cdifferential evacuationxe2x80x9d implies an evacuation method in which a certain region is divided into different pressure (vacuum) regions of more than two.
Further, through evacuation via the evacuation use groove portion on the table while coming close the table toward the bottom face of the sample chamber cover, differential evacuation on the upper face of the table can be performed, and even in a case when the inside of the sample chamber is not in high vacuum, the passage of the charged particle beams upto the sample can be kept in high vacuum. Further, when carrying in the sample, the above differential evacuation is impossible, therefore, for the purpose of maintaining a predetermined degree of vacuum in the column, the open and close cover which closes a hole portion forming the passage of the charged particle beams is provided.
Further, the present invention provides an evacuation use device which is characterized by comprising a table which is provided with a recessed portion for mounting a sample and a groove portion surrounding the recessed portion; a stage which holds the table and is displaceable in front and back, right and left and up and down directions together with the table; a member which covers above the table; and an evacuation use pipe which communicates with the groove portion and evacuates gas between the bottom face of the member and the top face of the table including the sample.
Preferably, the evacuation use device comprises a pressure gauge which permits measurement of pressure in a region surrounded by the member, the table and a passage of charged particle beams to be irradiated onto the sample.
Preferably, the member is provided with an open and close cover which opens and closes the passage of the charged particle beams to be irradiated onto the sample.
Preferably, the distance between the recessed portion and the groove portion provided for the table is selected more than the radius of a passage hole for the charged particle beams provided at the bottom face of the open and close cover.
Preferably, the pressure gauge is provided at the open and close cover.
Preferably, the evacuation use device is provided with a means which evacuates a region surrounded by the member, the table, the passage of the charged particle beams and the open and close cover, measures pressure therein with the pressure gauge and operates the open and close cover after the measured pressure reaches at a same level as in a passage other than the region of the charged particle beams.
Preferably, the sample table includes a sample up and down moving mechanism which is used when transporting the sample.
Preferably, an air pad which evacuates gas is provided on the upper face of the table at the outer circumferential side from the groove portion.
Preferably, the height of the upper face of the air pad is selected lower than the upper face between groove portion and the air pad on the table.
Preferably, the height of the upper face of the air pad is selected higher than the upper face of the table at the outer circumferential side from the air pad.
Preferably, a gas lubrication is performed between the upper face of the pad and the bottom face of the member and the table is slidably moved by making use of the bottom face of the member as a guide face.
Further, the present invention is to provide a circuit pattern forming apparatus which comprises a column for irradiating charged particle beams onto a sample and an evacuation use sample chamber in which the sample is placed and which evacuates gas around the placed sample to keep vacuum therein and wherein under the condition kept in vacuum the charged particle beams are irradiated onto the upper face of the placed sample to form a circuit pattern on the upper face of the sample, which is characterized, in that the evacuation use sample chamber comprises a sample chamber main body; a table which is provided with a recessed portion disposed in the sample chamber main body and for mounting the sample and a groove portion surrounding the recessed portion; a stage which holds the table and is displaceable in front and back, right and left and up and down directions together with the table; a sample chamber cover which covers above the sample chamber main body including the table; and an evacuation use pipe which communicates with the groove portion and evacuates gas between the bottom face of the sample chamber cover and the top face of the table including the sample.
Further, the present invention is to provide a circuit pattern inspection apparatus which comprises a column for irradiating charged particle beams onto a sample on which a circuit pattern is formed and an evacuation use sample chamber in which the sample is placed and which evacuates gas around the placed sample to keep vacuum therein and wherein under the condition kept in vacuum the charged particle beams are irradiated onto the upper face of the placed sample to inspect the circuit pattern on the upper face of the sample, which is characterized, in that the evacuation use sample chamber comprises a sample chamber main body; a table which is provided with a recessed portion disposed in the sample chamber main body and for mounting the sample and a groove portion surrounding the recessed portion; a stage which holds the table and is displaceable in front and back, right and left and up and down directions together with the table; a sample chamber cover which covers above the sample chamber main body including the table; and an evacuation use pipe which communicates with the groove portion and evacuates gas between the bottom face of the sample chamber cover and the top face of the table including the sample.